[CLC-816] Make the canvas feed live

JIRA: https://jira.media.berkeley.edu/jira/browse/CLC-816

This should make the canvas activity feed live in the notifications area. It does not attempt to deal with persisting the data infinitely, since that is likely to be revisited starting next sprint. With a well populated activity feed (like Tammi's, although anyone else can generate traffic on their own canvas feed), this should be sufficient to put in front of the designers to assist in their re-design of the notifications area.